Method of impregnating the base of friction elements



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' memos. m-nov'ax, creme-20m, oomorrcur, 'sssrenoaf nnmms mm. or zemenroa-r, comoncu'r, A conronamonog co This invention relates to a" method of I pregnating the base of friction elements, said base consisting essentially of fibrous asbestos, with a'suitable binder, and more particularly to the method of incorporating this binder with the base material.

- One of the usual methods of making friction'elements having an asbestos fibre base, consists primarily in introducing a suitable I0 binder substance into the raw material, which may be in theform of woven tape made from asbestos yarn, or in the form of blanks cut from a sheet of felted asbestos made on a wet machine. This binder sub- 75 stance, which may be asphalt,or a drying oil, is usually introduced by first dissolving or' thinning it with asuitable solvent, such as gasoline; then impregnatin the asbestos fibrous material therewith, an finally heat treating the impregnated material to drive off the solvent and allow the binder materialto coat the fibres and fill the interstices between the fibres, after which heat'treatment is continued, if necessary, to harden and toughen the binder substance.

The purpose of using the solvent is twofold. Firstto lower the viscosity of the binder in its primary form so that it may impregnate easily and thoroughly, which viscosity in the case of a solid asphalt, such as gilsonite, is very great, even at high temperatures'; and secondto dilute the binder substance so that when thorough impregnation of the base does take place, a too great quantity of binder will not be deposited in the fibres to melt and smear when the elements are later heated by friction in actual operation on a brake or in a clutch.- As noted above, the solvent usedis generall an organic liquid such as gasoline or henzo which by its nature actually dissolves and V thins asphaltic and oily substances. .lhese solvents are fairly expensive because of their method of manufacture from the raw materials containingor producing them, and the solvent cost in a process such as outlined above is generall a major part of the total saturant cost. hire risk is also an important factor wherever such volatile inflammable materials are used.

The method developed herein may consist essentially in utilizing a dispersion. ofthe desired binder. substances in water, which may be in the form either of a colloidal suspension or an emulsion, wherein'the average.

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particle size is preferably smaller 'tli'antbe openings between the fibres of the basematerial, and the'electrical charge on the particles may be of'such polarity that the dispersin'g medium and the dispersed particles. contained therein may easily enter and permeate the fibrous base without undue' filtration of the particles on the-surface.

A dispersion such as shown above may partake of all the necessary qualities of a solution except the molecularly small-particlesize in the latter. However I have found that a range of particles ofisides from: 0.2;;

to 0.05;. more or less, will easily penetrate 70 sired to fortify.

A dispersion oremulsion having the desirable characteristics mentioned above is. 1 not a new composition of matter, and may be produced by those skilled in the art of emulsions and dispersions b i the use of several mechanical devices, suc as the Plauson colloid mill, the Premier colloidmill, and more common comminutin devices such as ball mills, etc. The detaile methods-of production of this material are not relevant to the intent of this specification and therefore do not entail description.

Que method of utilizing this material for the production of brake lining may he as follows: The raw asbestos tape is preferably freed from naturally contained oily materials, which, if present, would hinder the entrance of the watery medium, by dissolving them out with a solvent and then drying out the solvent, or .by washing them out in an aqueous soap solution and drying out the water. The raw asbestos may be then allowed v tosaturate completely in a dispersion of gilsonite in water containing about 25% gilson its by weight, wherein the gilsonite particles preferably have an average diameter less than 0.5 1. and are charged negatively. After being completely saturated, and after the tiny gilsomte particles have flowed through allthe interstices with the aqueous medium, the tape is scraped so as to removeany surface excess of saturant, and then dried at say, 250 to 300 F. more or less, for a period of say,-one to two hours more or less, to remove the water, leaving about 10%15% gilsonite on the basis of the original weight. Upon removal from the dryer preferably while still hot,the saturated tape may. be passed between pressure rolls, and compressed ltd! l5 cept 12MMaximum v 'to the desired finished size. This'pressure and rolling, fluxes and softens the hot gllsonite, and causes the particles to unite into a continuous film uniformly disseminated 5 throu 'h'the fibres which then acts as a strong high friction, water-re ellant binder for the finished brake lining. t is not essential that the asphalt be entirely fluxed at this point, for heat and fricti n encountered in service 10 will also further the fluxing action.

the dispersion of a solid material in water.

This increased viscosity merely necessitates a longer saturating period. Also, this type of material usually needs no mechanical-fluxing as the particles are sufliciently mobile, when the water medium is removed, to flux automatically. Where drying oils or fluid asphalts are used, it is customary to subject the dried material to a further high temperature heat treatment to harden the binder,

, and thus make it more suitable for use in a friction element.

The intent of this specification as shown above, is to describe a novel. of introducing a water resisting binder into friction element base materials, wherein the commonly used method of dissolving and thinning the bindin substance with a suitable organic solvent as substituted therefor the-use of a water dispersion or emulsion of these substances having certain required characteristics as indicated above.

B the term waterproof binder as used in the claim I intend to include those binding substances disclosed in the foregoing specification.

I claim .as my invention:

A step in the process of producing friction elements comprising saturating a previously formed or fabricated asbestos mass with a waterproof binder dispersed in an aqueous vehicle wherein the binder particles are materially smaller in size than the pores in the fabricated fibrous mass,- and have a negative electric charge.

IZADOR J. NOVAK.

general method v 

